[skull]

Question:
6.5 grams of TlCl (thallous chloride) is added to 0.75L of water at room temperature to determine K_sp. some of the thallous chloride does not dissolve, and the solution is declared saturated. A 0.4L sample is decanted off and evaporated to dryness, The weight of the remaining thallous chloride is 1.2 grams. Determine the solubility of thallous chloride, aswell as the Ksp.

To determine solubility, I assumed that the first part of the experiment is irrelevant (the part where excess TlCl is added to 750 mL). The sample that was decanted off was saturated, so therfore no more TlCl could be dissolved. I then calculated the concentation and determined tha amount that could be dissolved in 1 litre (0.0125 mol/L according to my calculations). I then squared this value to get K_sp (according to the K_sp expression since it equals x²) My answer turned out to be 1.56x10^-4. However, when I checked with,
http://www.ktf-split.hr/periodni/en/abc/kpt.html
it shows a different value. Can anyone see where i went wrong?
thanks

 

[Borek]

Your calculations are correct. Can't access Croatian page you have mentioned atm, my sources give pK_so as 3.7 - close. Don't bother with the difference.

[skull]

Thanks!
The source that I mentioned gives a K_sp value of 1.86x10^-4 for TlCl, which is close enough I guess.